More than three and a half years after the initial release of ChatGPT, AI assistants are now used by millions of people around the world, and the competitive landscape is changing rapidly. While OpenAI’s chatbot is still the world’s most popular assistant, globally its market share has fallen below 50% for the first time as users migrate between different assistants such as Google’s Gemini, Anthropic’s Claude and xAI’s Grok, according to analyst firm Sensor Tower’s 2026 State of Artificial Intelligence report.
ChatGPT’s growth has been impressive. It became the fastest app in history to reach one billion monthly users, just like Sensor Tower reported this month. It’s worth noting that OpenAI counts weekly vigorous users, and most recently recorded 900 million of them in February. Chatbot continues to be the most popular AI assistant in the world with over 1.1 billion monthly users, followed by Gemini with 662 million and Claude with 245 million.
Until January, ChatGPT had over 50% market share, but by the end of May it had dropped to 46.4% thanks to the growth of Gemini (27.7%) and Claude (10.3%). Other assistants, including Grok, Perplexity, DeepSeek and Meta AI, have less than 5% market share.
Sensor Tower’s State of Artificial Intelligence report also shows that users are increasingly willing to switch between assistants. Specific events appear to be accelerating this behavior: for example, OpenAI’s deal with the US Department of Defense (DoD) in February resulted in a measurable raise in uninstalls, suggesting that what matters to users is brand trust and alignment with values, not just features. While much of Gemini’s momentum comes from integration with the broader Google tools ecosystem, Anthropic’s Claude has built a robust reputation for productivity applications and is approaching ChatGPT’s user retention rate.
According to Sensor Tower estimates, in the first half of 2026, people are expected to download almost 2.3 billion AI applications and spend over $4.2 billion on them. By comparison, spending in the first half of 2025 was $1.83 billion. This is a leap that suggests the industry is shifting its focus from pure growth to monetization. That said, both download and spend growth rates have slowed, indicating that the market may be maturing even as absolute numbers raise.
Regionally, Asia saw the first download decline of 3.3% in the first quarter of 2026, led by declines in China and India. Although Asia leads the world in total downloads, it trails North America and Europe in app spending – a split that matters to companies deciding where to invest in premium features and monetization.
In the US, users are gravitating towards AI assistants for productivity tasks and spending more on premium features. Across all platforms, average revenue per user has increased across the industry, but Claude stands out. Thirteen percent of Anthropic users pay for a subscription plan – the conversion rate is leading in this space and will be a metric worth watching for investors assessing which AI companies are generating sustainable revenue.
Sensor Tower estimates that hours spent on AI applications will raise from 17.2 billion hours in the first half of 2025 to approximately 36 billion hours in the first half of 2026. The top three assistants spend 89% of time spent on AI assistant applications. Meanwhile, adjacent categories such as AI companions or AI content generation applications remain fragmented and wide open to competition, presenting both a risk and an opportunity, depending on which player takes the first step.
OpenAI began experimenting with ads on ChatGPT in February. According to Sensor Tower, the company has gradually scaled the number of ads along with the share of users viewing them. Through May, ads were seen by an average of 17% of users per day – a number worth watching as ChatGPT’s monetization strategy evolves beyond subscriptions.
Software and Shopping are by far the largest advertiser categories on ChatGPT, followed by Media & Entertainment and Food & Dining.
As ChatGPT deepens shopping integration, it is increasingly sending referral traffic to retailers like Target, Walmart and Costco. As a result, Amazon, which blocked ChatGPT web crawlers, saw referral traffic stagnate from the platform.
This creates an opening for others. Sites like Walmart have their own AI assistants built in to support shoppers find products. While Amazon’s Rufus has seen steady growth in users, Walmart’s Spark is gaining ground. Sensor Tower also noted that Amazon customers who used Rufus spent more time in the app and converted at a higher rate than those who didn’t, suggesting that AI on the platform can significantly influence purchasing behavior when users actually utilize it.